It is known that monomers, such as ethylene, propylene, and other olefins, may be polymerized at high pressures in combination with high temperatures. Typically the polymerization reaction occurs within a reactor where the pressure ranges from about 20 MPa to in excess of 300 MPa. In situations when the pressure equals or exceeds 110 MPa, the polymerization reaction is considered a high pressure reaction thereby requiring a high pressure reactor. Exemplary high pressure reaction systems are disclosed in the following references: U.S. Pat. No. 3,725,378 to Chamberlin, U.S. Pat. No. 4,175,169 to Beals et al., and U.S. Pat. No. 6,673,878 to Donck.
Conventional systems for controlling high pressure polymerization processes include sampling and analyzing a product stream downstream of the reactor. These control systems are time intensive and analytical results are usually available only every 2 to 4 hours. In commercial scale polymerization processes, many thousands of tons of product can be produced in the time span of 2 to 4 hours. Accordingly, conventional control systems may result in the production of a large amount of off-spec product.